Free piston machine



Nov. 8, 1966 F. STELZER 3,

FREE PISTONMACHINE FiledMay s, 1964 ZSheetS -Sheet 2 INVENTOR UnitedStates Patent 3,283,752 FREE PISTON MACHINE Frank Stelzer, Elbestrasse59, Raunlieim, near Frankfurt, Germany Filed May 5, 1964, Ser. No.365,211 Claims priority, application Germany, May 6, 1963, H 49,061;Oct. 7, 1963, St 22,364 2 (Ilaims. (Cl. 123-46) The present inventionrelates to a free piston machine, and more particularly to a free pistonmachine operating according to the two cycle principle and being acombined prime mover and engine.

It is one object of the present invention to provide a combustion enginewhich is particularly suited for propelling vehicles or for drivingother machines.

Another object of the invention is to provide a free piston of simpleand economical construction which reliably operates.

Another object of the invention is to provide a free piston machine inwhich moving mechanical parts, such as cranks, connecting rods and crankshafts are omitted.

Another object of the invention is to provide a machine with a movableelement which is driven to produce power which is partly used for doingwork.

With these objects in view, the present invention relates to a freepiston machine which operates on the two cycle principle, and compressesa gaseous fuel before the same is ignited.

One embodiment of the invention comprises cylinder means having twocylinder spaces separated by a transverse wall; a piston means includingtwo pistons located in the cylinder spaces and a connecting portion ofsmaller diameter passing through an opening in the transverse Wall.

Each piston forms in the correlated cylinder space a compression chamberand a combustion chamber con tracting and expanding during reciprocationof the piston means.

Means for supplying fuel into the compression chan1- bers, means forexhausting burned gases from the combustion chambers, and passage meansfor connecting each compression chamber with a combustion chamber areprovided.

In the preferred embodiment of the invention, the two pistons have thesame diameter, and the connecting portion between the pistons, as wellas two end portions of the pistons have a smaller, and preferably equaldiameter. The end portions of the piston are advantageously guided incylinder portions at the ends of the cylinder means, and may be used aspump or compressor pistons.

In another embodiment of the invention, the entire piston means has aninner axially extending cavity narrower at one end than at the otherend, and preferably provided with a check valve, so that a fluidsupplied to the wider end of the cavity will be compressed oraccelerated at the narrower end ofthe cavity when the piston means isreciprocated.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompariying drawings, inwhich:

FIG. 1 is a diagrammatic cross-sectional view illustrating the shape ofa cylinder means and piston means in accordance with the principle ofthe present invention;

FIG. 2 is an axial sectional view of one embodiment of the invention,conventional elements being schematically illustrated for the sake ofsimplicity; and

Patented Nov. 8, 1966 FIG. 3 is an axial sectional view illustratinganother embodiment of the invention.

Referring now to the drawings, and more particularly to FIGS. 1 and 2, acylinder means 12 has walls which define an inner cavity 10 in which apiston means 14 is disposed for axial reciprocating movement. Pistonmeans 14 has two pistons 18, a connecting portion 16 of smaller diameterthan pistons 18, and two cylindrical end portions 20 located in cylinderportions which define cylinder chambers 28. The two cylinder spaces oflarger diameter formed by the cylinder means 12 are respectively dividedby the pistons 18 into axially outward located combustion chambers 26,and axially inward located compression chambers 24. The connectingportion 16 of piston means 14 is slidably guided in an opening 22 and,as shown in FIG. 2, piston rings 40 on connecting portion 16 preventcommunication between compression chambers 24. Piston rings 40 are alsoprovided on pistons 18 so that each compression chamber is separatedfrom the correlated combustion chamber located in the same cylinderspace.

The cylinder spaces 28 are closed by transverse end walls in which inletvalve means 44 and outlet valve means 46 are located.

In each combustion chamber 26, igniting means 42, such as a sparkplug,or a member permanently heated by the heat of the combustion, areprovided.

An outlet 38 for discharging combustion gases is pr0- vided in eachcombustion chamber spaced from the igniting means 42 in axial directionso that the respective outlet 38 is closed when piston 18 is in theposition shown for the left piston in FIG. 2.

An inlet means 30 for fuel, or fuel-air mixture, or other suitablefluid, is provided in each compression chamber 24 adjacent therespective outlet means 38.

A passage 34 connects each compression chamber 24 with the correlatedcombustion chamber 26, and has a slot-shaped port 32 in the respectivecompression chamber adjacent the central wall, and a slot-shaped port 36which opens into the respective combustion chamber.

The inlet means 30 are connected with a conventional fuel carburetor orfuel injection device, not illustrated.

The machine operates in the following mannerz The combustion chamber 26on the left of FIG. 2 is contracted to the minimum volume since thepiston means is in its left dead center position, or shortly before thesame. When the igniting means 42 have ignited the-com pressed fuel incombustion chamber 26, or if the com pressed fuel was ignited withoutigniting means due to its great volatility, for example, gasoline,piston means 14 is driven to the right as viewed in FIG. 2.

The left piston 18 first closes the inlet 30, then compresses thegaseous fuel in compression chamber 24, and finally presses the fuelthrough passage 34'when piston 18 has travelled far enough to uncoverport 36 of passage 34. The fuel flows in compressed condition intocombustion chamber 26.

During the same stroke the piston means 14 moves the right piston 18 tothe right to first close the outlet 38 and port 36, and to then compressthe already pre-compressed fuel in the right combustion chamber 26 untilarriving in the right dead center position where the compressed fuel inthe right combustion chamber 26 is ignited.

At the same same, the right piston 18 uncovers the inlet 30 so that afresh fuel mixture can enter the right compression chamber 24. At thesame time, the left piston 18 has arrived in its right dead centerposition closing port 32. In this manner, the piston means 14 isreciprocated in two cycles.

The end portions 20 of the piston means reciprocate at the same time inthe correlated cylinder chambers 28, and it will be understood that afluid entering through inlet valves 44 during movement of the pistonmeans in one direction will be discharged through outlet valves 46during a reciprocating stroke of the piston means in the oppositedirection. Since the discharge from the two pump chambers 28 takes placealternately, a fairly constant flow is assured.

FIG. 3 illustrates a modified embodiment of the invention, andcorresponding parts are indicated by like reference numerals. The pumpchambers 28 are omitted, and opeen cylinder portions 49 provided at theends of cylinder means 12. The piston means 14' is provided with longerend portions 50 which project out of the cylinder portions 49. Thepiston means 14' has an inner frusto-conical cavity 48 wider at theright end and narrower at the left end of piston means 14, a short widerportion 52 being provided at the narrow end of cavity 48.

When the piston is reciprocated due to the combustion of gases in thecombustion chambers 26, a fluid medium surrounding the right end ofpiston means 14' will be compressed or accelerated in cavity 48 whilepiston means 14 moves to the right. A check valve 53 arranged in cavity48 prevents the return of fluid during the stroke in the oppositedirection so that the fluid is pumped from the wider open end 50 to thenarrower end 52 of the cavity.

As compared with conventional two cycle motors with slot-shaped portsand transverse flow of the air, the machine of the invention has greatadvantages inasmuch as no connecting rods and crankshafts are required,and a single piston means operates in two combustion chambers to bedriven during opposite strokes. The moving mass is small, andconsequently a higher degree of compression, and a more exact timing canbe achieved than with conventional two cycle motors, particularly sincethe pre-compression takes place only in the compression chambers 24,whereas in known constructions, the precompression is effected alsowithin a crankshaft case. The compression chambers 24, in which the fuelis precompressed, have an exactly determined volume.

The power given to the piston means by the combustion of the fuel istransformed into work by the piston end portions or by the direct actionof the piston means, as explained with reference to FIG. 3. A singlepiston means is driven, and also operates to pump a liquid, or tocompress a gas. Of course, the power of the reciprocating piston meansmay be used in any other suitable manner. In the embodiment of FIGS. 2and 3 where a fluid is pumped, the fluid may be supplied to turbines,for example, to turbines located in the wheels of a vehicle so that allwheels are driven from the two cycle combustion engine of the invention.

In order to start the machines according to the invention, the operationis reversed, and a compressed fluid, for example, compressed air issupplied in intermittent and alternating thrusts into the chambers 28 ofthe machine so that the piston means is reciprocated and compresses thefuel mixture to start the regular operation.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types offree piston machines differing from the types described above.

While the invention has been illustrated and described as embodied in atwo cycle free piston double-acting combustion engine, it is notintended to be limited to the details shown, since various modificationsand structural changes may be made without departing in any way from thespirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can by applying current knowledgereadily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this inventionand, therefore, such adaptations should and are intended to becomprehended within the meaning and range of equivalence of thefollowing claims.

What is claimed as new and desired to be secured by Letters Patent is:

l. A two cycle free piston machine comprising, in combination, acylinder means having wall means forming two cylinder spaces having thesame diameter, said wall means including a transverse wall separatingsaid two cylinder spaces and having an opening connecting said cylinderspaces, said cylinder means including two cylinder portions at the endsthereof coaxial with said cylinder spaces; a piston means including twopistons having the same diameter and being respectively located in saidcylinder spaces, two cylindrical end portions slidable in said cylinderportions of said cylinder means, and a connecting portion having asmaller diameter than said pistons and passing through said opening insaid transverse wall,-each piston forming in the correlated cylinderspace a compression chamber and a combustion chamber, said chamberscontracting and expanding during reciprocation of said piston means;inner conical cavity means References Cited by the Examiner UNITEDSTATES PATENTS 735,863 8/1903 Duryea et a1 123-46 1,405,551 2/1922Nichols 123-46 1,741,731 12/1929 Nordensson 23056 2,067,358 1/1937Thornton 23035 2,178,310 10/1939 Pescara 230-56 3,170,406 2/ 1965Robertson 103-54 FOREIGN PATENTS 827,407 2/ 1960 Great Britain.

MARK NEWMAN, Primary Examiner.

WENDELL E. BURNS, Examiner.

1. A TWO CYCLE FREE PISTON MACHINE COMPRISING, IN COMBINATION, ACYLINDER MEANS HAVING WALL MEANS FORMING TWO CYLINDER SPACES HAVING THESAME DIAMETER, SAID WALL MEANS INCLUDING A TRANSVERSE WALL SEPERATINGSAID TWO CYLINDER SPACES AND HAVING AN OPENING CONNECTING SAID CYLINDERSPACES, SAID CYLINDER MEANS INCLUDING TWO CYLINDER PORTIONS AT THE ENDSTHEREOF COAXIAL WITH SAID CYLINDER SPACES; A PISTON MEANS INCLUDING TWOPISTONS HAVING THE SAME DIAMETER AND BEING RESPECTIVELY LOCATED IN SAIDCYLINDER SPACES, TWO CYLINDRICAL ENDS PORTIONS SLIDABLE IN SAID CYLINDERPORTIONS OF SAID CYLINDER MEANS, AND A CONNECTING PORTION HAVING ASMALLER DIAMETER THAN SAID PISTONS AND PASSING THROUGH SAID OPENING INSAID TRANSVERSE WALL, EACH PISTON FORMING IN THE CORRELATED SPACE ACOMPRESSION CHAMBER AND A COMBUSTION CHAMBER, SAID CHAMBERS CONTRACTINGAND EXPANDING DURING RECIPROCATION OF SAID PISTON MEANS; INNER CONICALCAVITY MEANS EXTENDING FROM ONE OF SAID CYLINDRICAL END PORTIONS TO THEOTHER OF SAID CYLINDRICAL END PORTIONS AND BEING WIDER AT ONE END THANAT THE OTHER END THEREOF WHEREBY DURING RECIPROCATION OF SAID PISTONMEANS A FLUID CAN BE COMPRESSED IN OR PUMPED THROUGH SAID CAVITY MEANS;MEANS FOR SUPPLYING FUEL INTO SAID COMPRESSION CHAMBERS; MEANS FOREXHAUSTING GASES FROM SAID COMBUSTION CHAMBERS; AND PASSAGE MEANS FORCONNECTING EACH COMPRESSION CHAMBER WITH THE CORRELATED COMBUSTIONCHAMBER.